1. Field of the Invention
The present general inventive concept relates to a display device and a driving method thereof. More particularly, the present general inventive concept relates to a display device that can be miniaturized and can reduce manufacturing costs, and a driving method thereof.
2. Description of the Related Art
A digital visual interface (DVI), which is a standard to transmit digital data generated in a personal computer (PC) to a monitor, has been mainly employed with a device that is connected to a PC, such as a projector for business, a commercial plasma display, and an electric board. Recently, the DVI has been introduced to an electronic appliance including a digital TV, a set-top box, etc.
Such a DVI standard has been developed in order to directly transmit digital data without complicated processes. Generally, digital data is transmitted according to complicated processes as follows: a PC generates digital data and converts the digital data into analog data to transmit to a display device, and then the display device converts again the received analog data into digital data.
In accordance with requests of content providers providing this digital data, service providers and electronic appliance providers employ DVI instead of various interfaces such as an IEEE 1394 and an analog connector.
To employ the DVI, a display data channel (DDC) is indispensable. The DDC is a standard that changes recognition information of a display device between a host device outputting image information such as a personal computer (PC) and a display device, and sets a display setting of the display device. The recognition information, for example, may indicate an attribute of the display device such as an optimal resolution.
The display device employing the DVI standard includes a DVI connector having a DDC channel, such as SDA and SCL, to transmit and receive the recognition information, such as extended display identification data (EDID).
Generally, the display device employing the DVI standard needs various functions besides its basic function in which the display device is connected to a PC to receive the processed image signal from the PC and display an image. The various functions include, for example, a function of displaying an image using an image signal output from an image reproducing device such as a DVD player.
Additionally, the display device needs functions of displaying an image using digital image information that is output from a host system, which provides image information, such as the PC and the DVD, and also using analog image information that is output from a PC.
Accordingly, when the digital image information and the analog image information are transmitted and received through the DVI connector, the appropriate recognition information corresponding to the signal transmission scheme should be output to the host device, since the recognition information of the display device corresponding to the digital signal transmission scheme and that corresponding to the analog signal transmission scheme are different from each other.
FIG. 7 is a schematic block diagram of a display device 10 according to a comparative example, and FIG. 8 is a view of an example of a switch 12 illustrated in FIG. 7.
Referring to FIG. 7, the display device 10 includes a DVI connector 11, a switch 12, a first memory 13, a second memory 14, a control unit 15 including a controller 15-1 and a storage unit 15-2, and a display 16.
In detail, the DVI connector 11 transmits and receives digital image information D_ID and the analog image information A_ID to and from external host devices 20 and 30, respectively. At this time, the display device 10 may transmit and receive the digital and analog image information to and from one host device such as a PC.
The switch 12 selectively provides the driving voltage VDD to the first memory 13 and the second memory 14 depending on a transmission scheme of the image information. The operations of the switch 12 are as follows.
When the display device 10 is connected to the first host device 20, a first transmission cable (hereinafter referred to as “cable 1”) may be connected to the DVI connector 11, which has a 24 pin DVI-D terminal transmitting and receiving the digital image information. Additionally, in order to connect the display device 10 to the second host device 30, a second transmission cable (hereinafter referred to as “cable 2”) may be connected to the DVI connector 11, which has a 15 pin D-SUB terminal transmitting and receiving the analog image information.
The connected terminals of the transmission cable 1 and the transmission cable 2 are different from each other. Accordingly, when transmission cable 2 is connected, some signal pins of the DVI connector 11 are not connected to transmission cable 2, and a certain pin among these signal pins is pre-set as a status check pin.
At this time, high voltage potential levels are basically applied to the signal pins of the DVI connector 11, and also to the status check pin. The potential levels of the status check pin are different between when the transmission cable 1 is connected and when transmission cable 2 is connected.
The switch 12 receives the potential levels of the status check pin, which are differently formed when transmission cable 1 is connected and when transmission cable 2 is connected, as a control signal CNT to perform switching.
For example, as illustrated in FIG. 8, when the status check pin of the DVI connector 11 is connected through transmission cable 1 to the switch 12, the status check pin is connected to a ground terminal GND of the first host device 20 and its status is changed to a low potential level. This low potential level is applied as a control signal CNT of the switch 12, and accordingly, a first switch element 12-1 is activated so that the driving voltage VDD is applied to the first memory 13 and the first memory 13 is activated.
In contrast, if the status check pin of the DVI connector 11 is connected through transmission cable 2, the status check pin is formed in a floating status and its high potential level is maintained. The high potential level is applied as a control signal CNT of the switch 12, and accordingly, a second switch element 12-2 is activated so that the driving voltage VDD is applied to the second memory 14 and the second memory 14 is activated.
The first memory 13 stores the recognition information corresponding to the digital image information, for example, digital EDID information, and the second memory 14 stores the recognition information corresponding to the analog image information, for example, analog EDID information.
Accordingly, one of the first memory 13 and the second memory 14 is selectively activated by the driving voltage VDD that is selectively provided by the switch 12. The digital and analog EDID information stored in each of the first memory 13 and the second memory 14 is read to the DVI connector 11 depending on the control signals output from the controller 15-1 and transmitted to the host devices 20 and 30.
By the above process, the host devices 20 and 30 determine the attribute of the display device 10 based on recognition information REC_D1 and REC_D2 output from the display device 10, and transmit control signals to the display device 10 to set an image quality mode Q_mode of the display 16, in response to the recognition information REC_D1 and REC_D2. The image quality mode Q_mode set by the display device 10 is stored into the storage 15-2.
The host devices 20 and 30 transmit the digital or analog image information D_ID or A_ID to the display device 10 according to the digital or analog transmission scheme, and display a certain image on the display 16 in response to the stored image quality mode Q_mode and the digital or analog image information D_ID or A_ID.
Generally, the first memory 13 and the second memory 14 are configured as a non-volatile memory such as an EEPROM to store the recognition information even when power is not supplied to the display device 10.
In the case of an analog transmission scheme, the recognition information is read from the second memory 14 so that the image information can be output from the second host device 30, according to the characteristics of the analog transmission scheme, even when power is not supplied to the display device 10. However, in the case of a digital transmission scheme, the recognition information cannot be read from the first memory 13 when power is not supplied to the display device 10. In this case, the image information itself may be blocked from being output from the first host device 20 so that separate memories 13 and 14 are provided as illustrated in FIG. 8 to prevent this problem.
However, if each memory is provided to store the recognition information which corresponds to each transmission scheme depending on the transmission scheme of the image information, it is difficult to miniaturize the display device and reduce its manufacturing costs.